• Ultraviolet Photography

pi camera redux with LodestarC

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#1 dabateman

    Da Bateman

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Posted 17 July 2021 - 06:44

I have finally figured out how to make the Lodestar X2 Color sensor portable with the Raspberry pi.
Downloading the latest image of Astroberry worked, as it has the drivers for the Starlight Xpress (SXCCD) cameras. So with this flashed to a micro SD chip, the pi becomes an Astrophotography toy. But included are working versions of some free software with the drivers needed to run the Lodestar color or monochrome cameras.

So now I can use PHD2 to capture images using the Lodestar x2C camera connected to the Pi with a USB cable. I also needed a touch screen keyboard, to type in file names to save images. But PHD2, allows you to change the shutter speed from 0.01 to 30 seconds with simple pull down menu and you get a live view for focusing and stop button to freeze the frame. So now I have a new camera setup that looks like this:
Attached Image: 20210716_153820.jpg

I have mounted the Lodestar under the main plate and it has a 12.5mm C-mount lens attached. The sensor size I think is the exact same as the pi HQ camera. The Lodestar is a CCD sensor with only 752 x 580 pixels with CMYG color layout. I have two 12.5mm lens, which worked well for the test today, but I still managed to frame differently, do to the heat and trying to stay in the shade.

I added a 2mm UG1 filter and 2 mm S8612 filter to match the UV HQ pi camera to take a quick test image. This image is taken outside with sunlight as the light source at 1000F with 300% humidity. Only slightly joking about that last part, was 100F, and 60% humid today. So my dandelion died within a minute of picking out from the shade. So did the other flower.
Base gain, 1/100 shutter speed with F4 on the 12.5 mm lens with 2mm UG1 and 2mm S8612 on Lodestar processed with Starlight live on Windows after collecting the raw .Fit file:
Attached Image: Image_2021.7.17_02.00.03.jpg

Yes It looks like I missed focus on the LodestarC image. I definitely need more practice using it.

Comparison is base ISO, 1/13 second shutter speed f1.3 on the 12.5 mm lens with 2mm ZWB2 and 2mm S8612 for the pi HQ camera (filters are in the camera so any lens can be added):
Attached Image: 20210715_151022_auto.jpg

I still need to workout how best to use the Lodestar, now that its portable its more fun to play with. Its low resolution and I don't think I captured it at its best here. Next should be a color chart in sunlight to really see the crazy color difference. I would like to see how the CMYG sensor shows false UV colors and compares to the typical RGGB sensor.

But you can see how sensitive it is. These images differ by 6 stops!

Edited by dabateman, 17 July 2021 - 07:00.

#2 colinbm


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Posted 17 July 2021 - 07:59

Looks fascinating Dave.

#3 Stefano


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Posted 17 July 2021 - 11:32

Very interesting. The colors look more or less similar now, you have a yellow dandelion in both images. Probably in deeper UV the colors will be different.

You should try IR too and see if you get a palette different from the usual yellow-blue after you apply a white balance.